The development of manufacturing, restoration and hardening technologies for parts operating in the soil medium, and above all for structural elements of tillage machines requires preliminary tests of materials in use for abrasive wear resistance. The above-mentioned extends to heat-treated steels. However, the existing methods and devices for carrying out such studies do not allow to cover the whole complex of problems. So, there are no methodologies allowing to carry out accelerated comparative tests of several heat-treated samples simultaneously with different parameters of mode, while maintaining the identity of tests at any time. As a result of considering a number of constructive schemes, a device with five experimental samples mounted on its cylindrical form framework is proposed. The tests are carried out by means of its vertical axis rotation in abrasive medium. The article presents the proposed device as an actual product. A method of experimentation has been worked out for the medium, which is a sandy loam soil with gravel inclusions. The developed method and equipment allow to carry out the wear tests for studying of abrasion resistance of at least five samples of different hardness, for conducting of the research under same conditions for all test materials at any time, for providing the accuracy and comparability of the results.
It was shown that wear dynamic of renewed blades depends on operation time linearly. Deterioration intensity is maximal in debugging and operating periods, but in deterioration process it assumes stabile behavior.
When reinforcing the surfaces of the working bodies of tillage tools, they are surfaced with electrodes with a low-carbon rod. The surface in contact with the soil is not subjected to heat treatment. Recently, thermal hardening of local parts has been used. (Research purpose) The research purpose is in studying the transformation of the microstructure of 65G heat-strengthened steel deposited by an electrode with a low-carbon rod, as well as the specifics of the microhardness distribution in this section. (Materials and methods) Investigated in the cross-section of the structure of the deposited area by the standard method, consisting in the preparation of microsections, etching and directly microanalysis. (Results and discussion) The transformation of the microstructure of heat-strengthened steel 65G deposited by an electrode with a low-carbon rod is complex due to the specificity and versatility of the phase transformations that occur during its formation. The microhardness distribution plot in the cross-section of the surfacing area has a complex configuration, determined by the variety of structural components, the presence of deformation processes during crystallization and solidification, and the presence of preliminary thermal hardening of the base metal. (Conclusions) Increased values of the hardness of individual areas contribute to an increase in the abrasive wear resistance of the part. The presence of the fusion zone ensures the resistance of the deposited area to cracking. The zone of thermal influence has four clearly distinguishable areas: the drop in microhardness; the stable values according to the Vickers method; the near-shock zone; the fusion zone. The microhardness of the weld surface of the cushion is 410 Vickers or 42 Rockwell, which creates conditions for increasing the wear resistance of the surface friction. The use of electrodes with a low-carbon rod is advisable when conducting surfacing reinforcement of heat-strengthened steels.
In spite of wide use of the polymer adhesive composite disperse materials in various industries, they aren’t in demand as materials for the restoration and strengthening of the friction surfaces of parts of tillage machines. The reason lies in the obscurity of their tribotechnical properties. First of all, these materials include the composites based on epoxy components filled with waste fractions of abrasive wheels. Therefore, the wear pattern during the testing time, as well as the effect of testing time on wear-out rate of the composite and of epoxy composition without filler have been investigated. The studies were of comparative nature and were carried out using an individual method. The content of this method is testing of 16 samples simultaneously in the same conditions at any time of the experiment. The epoxy composition (100 weight parts of ED-20 epoxy and 7 weight parts of hardener) and the composite comprising such epoxy composition and abrasive waste fractions of grinding wheels in the ratio of 30% to 70% respectively have been studied. The results of the experiments show that the dependence of wear and wear-out rate on testing time has a classic nature, identified previously in number of studies. The presence of dispersive component in composite in the form of waste fractions of abrasive wheels has a positive effect on reducing of its wear-out rate. It is established that the wear-out rate of composite is 1.5 times less than the wear-out rate of epoxy composition without filler, providing thereby the possibility of its use as an abrasion-resistant repair material for restoration of parts.
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